This invention relates to wireless communication systems and, more particularly, to a wireless communication system for electronic devices that are located in an enclosed space having a high likelihood of multi-path transmission and reception problems and that are subject to electromagnetic compatibility (EMC) and electromagnetic interference (EMI) requirements.
Autonomous underwater vehicles (AUV""s), torpedoes, automobiles, aircraft, test equipment suites, etc., typically require extensive cables, optical fiber, wiring harnesses, and/or connectors to support communications and control signals. These signals are typically sent from one electronic device across the cables or optical fiber to one or more other electronic devices. In these applications, the communicating electronic devices are typically sensors, motors, valves, actuators, processors, communications devices, navigation devices, etc. The electronic devices are generally located inside an enclosure such as a hull of an AUV, torpedo or aircraft, a metallic body of an automobile, a cabinet for test equipment, etc.
The cable and/or optical backbones, harnesses and connectors occupy the interior space of the enclosure which could otherwise be used to carry payload, other electrical sensing or control devices, and/or additional passengers. The cable and/or optical fiber, harnesses and connectors also increase the weight of the AUV, torpedo, automobile and aircraft which reduces the range and efficiency of the vehicle.
When extensive cabling and/or optical backbones are employed in the enclosure, diagnosis of electrical faults becomes more problematic. The cables and/or optical fiber are generally run together so that identification of one of the cables or optical fibers can be difficult. Because the turn-around time for repairs increases due to the increased troubleshooting time required, the uptime of the AUV, torpedo, aircraft, automobile, or test equipment decreases. When sensor configuration changes and/or equipment upgrades are required, routing additional cables and/or optical fiber can be very difficult due to the existing cabling and/or optical backbone.
To ensure robust electromagnetic compatibility (EMC) and electromagnetic interference (EMI) behavior, cables often require expensive shielding, particularly when the cables run adjacent a power source or other cables. Cables that are routed through an aperture in a bulkhead often wear prematurely due to abrasive contact with corners of the aperture. Premature wear can cause an intermittent short circuit or an open circuit which can be difficult to diagnose. In addition, cables and optical fiber also can require special connectors which can be expensive.
For example, an AUV typically includes a vehicle control processor (VCP) which is connected to a power supply such as a battery and to one or more power distribution units (PDU). The PDU, in turn, are typically connected to one or more sensors that monitor temperature, salinity, inertia, speed, spatial orientation, and/or pressure. The PDU can also be connected to the motor of the AUV, valves associated with ballast tanks, and actuators associated with the dive planes or rudder. The PDUs relay control and sensor information to the VCP where decisions are made. As can be appreciated, the length and weight of cable and/or optical fiber that is required to interconnect the valves, sensors, VCP and PDU can be significant. The interconnections are often made more difficult by firewalls or bulkheads that separate the valves, sensors, motors, battery, VCP and PDU.
A wireless, backboneless communication system according to the present invention transmits, receives, and repeats radio frequency signals inside an enclosure which has a high likelihood of multi-path transmission and reception problems. The enclosures can be the hull of a torpedo, autonomous underwater vehicle, or aircraft, the body of an automobile, or a test equipment enclosure. First and second electronic devices are located inside the enclosure. A first transmitter/receiver and repeater is connected to the first electronic device. The first transmitter/receiver transmits spread spectrum signals generated by the first electronic device and receives spread spectrum signals. A second transmitter/receiver is connected to the second electronic device. The second transmitter/receiver transmits spread spectrum signals generated by the second electronic device and receives spread spectrum signals.
Preferably, the first and second transmitter/receivers operate at low frequencies between 100 and 900 MHz. Additionally, the first and second transmitter/receivers operate at low power which is above a thermal noise threshold of the wireless communication system and below EMC/EMI standards.
In one preferred embodiment, the data spread rate of the spread spectrum signals is approximately 10:1 and the first and second transmitter/receivers operate between 100 and 400 MHz.
In another preferred embodiment, the first electronic device is a vehicle control processor. The enclosure is a hull of an autonomous underwater vehicle (AUV). The second electronic device is a power distribution unit. The hull preferably includes a first bulkhead that separates the hull into first and second sections. The first electronic device and the first transmitter/receiver are located in the first section. The second electronic device and the second transmitter/receiver are located in the second section.
If the bulkhead is made of a metallic material, the bulkhead preferably includes an aperture filled with a dielectric material. A dipole penetrator is located in the dielectric and extends outwardly from opposite sides of the dielectric. The dipole penetrator reduces signal attenuation between the first and second transmitter/receivers.
In another embodiment, the PDU communicates with a sensor for measuring an environmental characteristic, an actuator for controlling at least one of a dive plane and a rudder, and a valve associated with a ballast tank.
In yet another preferred embodiment the enclosure is a hull of an aircraft, and the first electronic device is an audio/video server. The second electronic device is an audio/video playback device that is located adjacent a passenger seat.
In still other preferred embodiments, the wireless communication system according to present invention is located inside an automobile or in a test equipment enclosure.
The various preferred embodiments of the wireless communication system according to the present invention allow wireless transmission and reception of signals inside an enclosure without significant multi-path problems. By reducing or eliminating cables, optical fiber, connectors and shielding, additional interior space inside the enclosure becomes available and allows increased payload, increased electronic devices, and/or reduced weight.